1. Field of the Invention
This invention relates to a housing of a sirocco fan widely used in an air conditioner or every field requiring a blowing operation of hot air or cold air, and more particularly to a suction structure of a sirocco fan housing, which is capable of improving blowing efficiency of a sirocco fan and reducing suction noises of the fan.
2. Description of the Prior Art
Generally, a prior art sirocco fan housing comprises a pair of right and left side plates 1, 1 and scroll plate 2, as shown in FIG. 1 of the accompanying drawings. One of the side plates 1 is formed with a suction opening 1a for intaking air into a sirocco fan 3, and the other is provided with a motor 5 for driving the fan 3, a motor securing plate 6 and a plurality of vibration proofing members 7. Such a sirocco fan housing is of a snail shell-like shape including a throttle portion 2a provided by a bent portion of the scroll plate, a scroll portion 2b and a discharge opening 2c provided by an open top thereof.
With this construction, if the fan driving motor 5 is driven to rotate the sirocco fan 3 secured to a motor shaft 5a, as shown in FIG. 2, centrifugal force is exerted upon air existing in the interior 3b of the fan by vanes 3a of the sirocco fan, so that negative pressure is created in the interior of the fan to intake ambient air into the interior through the suction opening 1a formed in the sirocco fan housing. Then, the sucked air is expelled toward the discharge opening 2c, as shown by the arrows, with an increased flow velocity by virtue of the vanes 3a of the sirocco fan rotated by the driving force of the motor 5. At this time, the expelled air is in part accumulated in the scroll portion 2b due to the throttle portion 2a so that dynamic pressure produced by the air flow velocity is converted into static pressure, then guided to the discharge opening 2c and discharged therethrough to the exterior.
In this prior sirocco fan 3, however, since according to a characteristic of the fan, a fluid intake is in the direction of the rotary shaft of the fan, undergoes a 90.degree. change of direction to flow radially, and then is discharged through the discharge opening 2c, a dead zone 4, as drawn by oblique lines in FIG. 2, is formed at a suction opening side forward end portion 3c of the fan 3 due to inertia of particles entrained in the air, so that a suction passage may not be established thereat. The extent of the dead zone corresponds to 20 % .about.30% of the length of each vane. Moreover, since the pressure of the exterior of the sirocco fan 3 is higher than that of the interior, great vortex flows as shown by the arrows in FIG. 2 are produced near the dead zone 4, i.e., at the forward end portion 3c of the fan, resulting in a static pressure loss, a lowering of efficiency of the fan and generation of flowing noises. Especially, since the suction passage may not be established at the forward end portion 3c, the circumferential area of the portion must be compensated to the extent of the dead zone such that each vane becomes longer than it needs, thereby leading to a wider sirocco fan.